Semi-conducting device



May 3, 1955 M. CONRAD SEMI-CONDUCTING DEVICE Filed Dec. 51, 1952 VFIG.I

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V INVENTOR. MATTHEW CONRAD AGENT United States Patent SEMI-CONDUCTINGDEVICE Matthew Conrad, Philadelphia, Pa., assignor to Stromberg-CarlsonCompany, a corporation of New York Application December 31, 1952, SerialNo. 329,025

4 Claims. (Cl. 29-253) My invention relates to a method of makingsemiconducting devices of the point-contact type, and more particularlyto point-contact semi-conductive devices of the coaxial class.

Coaxial semi-conducting devices known heretofore have been made bycutting a thin wafer of semi-conductive material, placing it in a tube,and bringing a point contact, or cat whisker, into contact with eachside of the semi-conducting wafer. This method has been costly becauseconsiderable semi-conductive material has been lost in the cuttingprocess, and expensive jigs and fixtures are required to set the pointsin the proper place. In addition, the wafer method of constructionproduces variations from unit to unit because of difficulty in holdingdimensions and because of the difficulty in controlling the exactcomposition of the semi-conductive material.

It is therefore an object of my invention to provide a method of makingsemiconductive devices which is relatively inexpensive, due to savingsin material costs and improved accuracy in contact setting.

It is another object of my invention to provide a semiconductive devicehaving more uniform characteristics which may be controlled throughcloser control of di mensions, particularly thickness, and throughcontrol of the composition of the semi-conductive material.

Further objects and advantages of my invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to theaccompanying drawing in which Fig. 1 is useful in explaining a step inthe method I have invented;

Fig. 2 is a top view of a semi-conductive device produced by thepreferred version of the method I have invented; and

Fig. 3 is a section, taken along line 3-3, of the semiconductive deviceshown in Fig. 2.

In practicing my invention, I prefer to embed an elongated conductor,such as a wire 1, in a mass, or bead, of insulating material 2. Thelatter is preferably composed of a refractory material, such as glass.Furthermore, I prefer that wire 1 be made of platinum.

The next step in my invention is to cleave the assembly formed by wire 1and head 2 into two portions along a plane perpendicular to thelongitudinal direction of wire 1. I have indicated this plane in Fig. lby symbols P-P.

Next I cause the cleaved surface of each portion of bead 2 to bedepressed below the respective cleaved ends of wire 1. I prefer to dothis by selectively etching away the cleaved surface of bead 2 withoutaffecting wire 1. As a result, wire ends 3 and 4 project beyond theetched surfaces which are indicated by dashed lines 5 and 6,respectively.

I prefer that ends 3 and 4 now be given a substantial degree ofpointedness, preferably by selectively etching Tree H: them with anetchant which does not attack the material of bead 2.

After each portion has been prepared, a conductive film, such as gold,may be applied to each etched surface of the insulating material. Thisconductive film may be, for example, gold, and is applied according tomy invention in insulated relationship with the projecting ends 3 and 4.The conductive films are indicated in Fig. 3 by reference numerals 7 and8. I prefer that these films be applied by vacuum evaporation, althoughthose' skilled in the art can readily understand that other methods maybe used. I prefer that layers 7 and 8 have portions 9 and 10 extendingaround at least a portion of the outer periphery of the bead material asshown in Fig. 3.

To prevent the conducting film from being deposited on ends 3 or 4 ofthe conductor, I may preferthat a drop of insulating material be placedover the end before the vacuum evaporation or similar process is accomplished. After application of the conductive film,

' the insulating material may be removed. For example,

the insulating material may be polymethyl methacrylate dissolved inethylene dichloride. After deposition, the metal deposited on thepolymethyl methacrylate may be sufiiciently removed to allow theapplication of ethylene dichloride, which then dissolves the remainingmaterial and so exposes the end of the conductor.

Next a film of semi-conductive material is deposited over the resultingexposed surface of the conductive film and of the conductor end in thecase of each portion. I prefer that the semi-conductive material begermanium, and that it be deposited by vacuum evaporation, carbonylgas-plating, or an equivalent suitable process. I have found that alayer of germanium from 0.0001 to 0.0005 inch in thickness may be soproduced. It is to be noted that the deposition processes mentionedenable the purity of the semi-conductive film to be controlled much morereadily than is the case with germanium crystallization processesemployed heretofore. The slight impurities in the germanium necessaryfor proper semi-conductor device operation tend to be nonhomogeneouslylocated in the latter case, Whereas in the film-deposition stepcontemplated by my invention, the percentage of these impurities presentmay be readily controlled along with the amount of germanium.

When both portions of the original assembly have been coated withconductive and then semi-conductive films, they are ready for assembly.I prefer that this assembly be accomplished by pressing both portionsinto a conductive tube 11. It will be noted that conductive tube 11,which may be of brass, provides means for securing both portions in aposition where the semi-conductive films of both portions are inintimate contact with each other, while simultaneously making contactwith conductive films 7 and 8 at circumferential bands 9 and 10. Thoseskilled in the art can readily appreciate that any conventional meansfor making contact to the conductors having ends 3 and 4 and to tube 11may be employed.

While I have shown and described my invention as applied to a specificversion thereof, other modifications will readily occur to those skilledin the art. I do not, therefore, desire my invention to be limited tothe specific method illustrated and described, and I intend in theappended claims to cover all modifications within the spirit and scopeof my invention.

What I claim is:

l. The method of producing a semi-conductor device which comprises thesteps of embedding a longitudinal conductor in a mass of insulatingmaterial to form an assembly; cleaving said assembly into two portionsalong a plane perpendicular to the longitudinal direction of saidconductor; selectively etching the cleaved surface of each said portionwithout affecting the conductor therein, whereby a conductor end is leftprojecting from each said cleaved surface; depositing a film ofconductive material over each said cleaved surface in insulatedrelationship with the conductor end projecting therefrom; depositing, inthe case of each said portion, a continuous film of semi-conductivematerial over the resulting exposed surface of said conductive film andsaid conductor end; bringing the exposed surface of said semi-conductivefilm and said conductor end; bringing the exposed surface of saidsemi-conductive film of each said portion into intimate contact withthat of the other said portion; and securing said portion in theposition so established.

2. The method of producing a semi-conductor device which comprises thesteps of embedding a longitudinal conductor in a mass of insulatingmaterial to form an assembly; cleaving said assembly into two portionsalong a plane perpendicular to the longitudinal direction ofsaidlconductor; selectively etching the cleaved surface of each saidportion without affecting the conductor therein, whereby a conductor endis left projecting from each said cleaved surface; selectively etchingeach said projecting end to substantial pointedness; depositing a filmof conductive material over each said cleaved surface in insulatedrelationship with the conductor end projecting therefrom; depositing, inthe case of each said portion, a continuous 'film of semi-conductivematerial over the a resulting exposed surface of said conductive filmand said conductor end; bringing the exposed surface of saidsemiconductive film of each said portion into intimate contact with thatof the other said portion; and securing said portion in the position soestablished.

3. The method of producing a semi-conductor device which comprises thesteps of embedding a longitudinal conductor in a mass of insulatingmaterial to form an assembly; cleaving said assembly into two portionsalong a plane perpendicular to the longitudinal direction of saidconductor; selectively etching the cleaved surface of each said portionwithout affecting the conductor'therein, whereby a conductor end is leftprojecting from each said cleaved surface; depositing a film ofconductive material over each said cleaved surface in insulatedrelationship with the conductor end projecting therefrom; depositing, inthe case of each said portion, a continuous film of semi-conductivematerial over the resulting exposed surface of said conductive film andsaid conductor end; bringing the exposed surface of said semi-conductivefilm of each said portion into intimate contact with that of the othersaid portion; and securing said portions in the position so establishedwhile simultaneously making contact with at least one of said conductivefilms.

4. The method of producing a semi-conductor device which comprises thesteps of embedding a longitudinal conductor in a mass of insulatingmaterial to form an assembly; cleaving said assembly into two portionsalong a plane perpendicular to the longitudinal direction of saidconductor; selectively-etching the cleaved surface of each said portionwithout affecting the conductor therein, whereby a conductor end is leftprojecting from each said cleaved surface; selectively etching each saidprojecting end to substantial pointedness; depositing a film ofconductive material over each said cleaved surface in insulatedrelationship with the conductor end propecting therefrom; depositing, inthe case of each said portion, a continuous film of semi-conductivematerial over the resulting exposed surface of said conductive film andsaid conductor end; bringing the exposed surface of said semi-conductivefilm of each said portion into intimate contact with that of the othersaid portion; and securing said portions in the position so establishedwhile simultaneously making contact with at least one of said conductivefilms.

References Cited in the file of this patent UNITED STATES PATENTS

1. THE METHOD OF PRODUCING A SEMI-CONDUCTOR DEVICE WHICH COMPRISES THESTEPS OF EMBEDDING A LONGITUDINAL CONDUCTOR IN A MASS OF INSULATINGMATERIAL TO FORM A ASSEMBLY; CLEAVING SAID ASSEMBLY INTO TWO PORTIONSALONG A PLANE PERPENDICULAR TO THE LONGITUDINAL DIRECTION OF SAIDCONDUCTOR; SELECTIVELY ETCHING THE CLEAVED SURFACE OF EACH SAID PORTIONWITHOUT AFFECTING THE CONDUCTOR THEREIN, WHEREBY A CONDUCTOR END IS LEFTPROJECTING FROM EACH SAID CLEAVED SURFACE; DEPOSITING A FILM OFCONDUCTIVE MATERIAL OVER EACH SAID CLEAVE SURFACE IN INSULATEDRELATIONSHIP WITH THE CONDUCTOR END PROJECTING THEREFROM; DEPOSITING, INTHE CASE OF EACH SAID PORTION, A CONTINUOUS FILM OF SEMI-CONDUCTIVEMATERIAL OVER THE RESULTING EXPOSED SURFACE OF SAID CONDUCTIVE FILM ANDSAID CONDUCTOR END; BRINGING THE EXPOSED SURFACE OF SAID SEMI-CONDUCTIVEFILM AND SAID CONDUCTIVE END; BRINGING THE EXPOSED SURFACE OF SAIDSEMI-CONDUCTIVE FILM OF EACH SAID PORTION INTO INTIMATE CONTACT WITHTHAT OF THE OTHER SAID PORTION; AND SECURING SAID PORTION IN THEPOSITION SO ESTABLISHED.